Conventionally, as shown in FIG. 5, in formation of insulating films or conductive films on wafers using CVD equipment and RIE (Reactive Ion Etching) equipment in a plurality of processing stations, such as multiple chambers, a processing gas is uniformly supplied to gas dispersing devices 2a to 2e respectively provided at the processing stations for equalized film formation rates, etching rates and the like in the respective processing stations. Specifically, processing gas supply sources 1a to 1e are respectively provided for the gas dispersing devices 2a to 2e, and sets of automatic flow rate controllers (AFC) 3a/4a/5a/6a to 3e/4e/5e/6e for automatically controlling the supply amounts of the processing gases are respectively provided for the processing gas supply sources 1a to 1e.
However, if the number of the gas dispersing devices 2a to 2e is increased, the number of processing gas supply sources 1a to 1e, the AFCs 3a/4a/5a/6a to 3e/4e/5e/6e and the like must be increased to a number corresponding to the number of the gas dispersing devices 2a to 2e, and consequently, the above construction has the disadvantages of increasing the cost and of complicating the maintenance of the equipment.
In analyzing the above problem, it may be considered that the processing gas supply sources 1a to 1e are united and also that the processing gas is branched into the gas dispersing devices 2a to 2e; however, since the conductances of respective branch pipings including the gas dispersing devices 2a to 2e are usually different from each other, it is difficult to uniformly supply the processing gas into each of the gas dispersing devices 2a to 2e. Also, even if the conductances of the branch pipings including the gas dispersing devices 2a to 2e are similar to each other, in the case of continuously executing the processing, it often occurs at the initial and final stages that the processing gas is supplied only to a portion of the gas dispersing devices and the supply of the processing gas to the remaining portion of the gas dispersing devices is stopped, which also affects the total amount of the processing gas to the gas dispersing devices. Namely, in the above case, the total amount of the processing gas will fluctuate more than where the processing gas is supplied to all of the gas dispersing devices 2a to 2e. Therefore, the film formation rate and the like are changed, thereby making it impossible to maintain uniformity of the thickness of the formed film.
Taking the above problems into consideration, the present invention has as its object provision of a semiconductor fabrication system capable of supplying equal amounts of a processing gas, for film formation or etching, from one gas supply source to the various processing stations, and thereby achieve uniform wafer processing at each processing station.